A new sesquiterpene lactone, namely, eupachiilide A (1), as well as two known sesquiterpene lactones, eupachinilide B (2), and eupalinilide G (3), were isolated from the whole plant of Eupatorium chinense L. The new structure was elucidated by spectral methods, especially 2D NMR techniques. The three natural compounds were all Michael addition acceptors, whose electrophilic moiety could react with the nucleophilic residues of the relevant active site and produce a variety of bioactivities. Eupachiilide A demonstrated potent cytotoxicity against two TNBC cell lines.

A new sesquiterpene lactone, namely, eupachiilide A (1), as well as two known sesquiterpene lactones, eupachinilide B (2), and eupalinilide G (3), were isolated from the whole plant of Eupatorium chinense L. The new structure was elucidated by spectral methods, especially 2D NMR techniques. The three natural compounds were all Michael addition acceptors, whose electrophilic moiety could react with the nucleophilic residues of the relevant active site and produce a variety of bioactivities. Eupachiilide A demonstrated potent cytotoxicity against two TNBC cell lines.

Introduction Innovative strategy is urgently needed to precisely discover novel natural products as lead compounds for development of new drugs against orphan diseases such as triple-negative breast cancer (TNBC). Herein, we describe a targeting pharmacophore with probe-reactivity-guided strategy for the discovery of electrophilic sesquiterpene (ES), a class of bioactive natural product. Objective This study aimed to identify pharmacophore, based on pharmacophore with probe-reactivity-guided strategy for precisely discovering ESs from ethyl acetate extract of Eupatorium chinense L. (EEEChL) Methodology MTT assay combined with ultra-performance liquid chromatography (UPLC) analysis was used to identify pharmacophore. UPLC-mass spectrometry (MS) was applied to carefully compare the intrinsic reactivity characteristics of two chemoselective nucleophilic probes: glutathione (GSH) and 4-bromothiophenol (BTP) reaction with ESs. ESs was isolated and identified from EEEChL by phytochemical methods. Furthermore, stoichiometric ratio and binding site of one typical ES 8 beta-[4 '-hydroxytigloyloxy]-5-desoxy-8-desacyleuparotin (HDDE) reaction with BTP were studied by UPLC-quadrupole time-of-flight (Q-TOF)-MS and two-dimensional nuclear magnetic resonance (NMR). Results Eleven ESs were identified from EEEChL, MTT assay illustrated that all of the 11 ESs possess fairly good anti-TNBC activity Conclusions Electrophilic groups were confirmed as pharmacophore of bioactive compounds contained in EEEChL. An optimised halogenated aromatic probe BTP furnishes ES-BTP conjugates that are highly conspicuous via MS by virtue of a unique isotopic bromine signature, conjugates also have a considerable separation on C18 column. The new probe-reactivity-guided strategy can effectively improve the traditional bioassay-guided approaches, and significantly increase the probability of obtaining designated bioactive compounds.